This is a gallery, created with the default WordPress Gallery Option. The Image size of gallery pics is set automatically when the theme is activated, all you have to do then is to insert a gallery with a max of 7 columns to make it look like the one below…

Gallery with Preview

Small Thumb Gallery

You can choose which Preview Image size you want to display and also how many thumbnails should be displayed within one row. Also notice the subtle animation effect that starts once the visitors screen has reached the Galleries, to draw his attention :)